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Antibiotic Treatment Response of Chronic Lung Diseases ofAdult Sheep in the United Kingdom Based uponUltrasonographic Findings

Citation for published version:Scott, P 2014, 'Antibiotic Treatment Response of Chronic Lung Diseases of Adult Sheep in the UnitedKingdom Based upon Ultrasonographic Findings', Veterinary Medicine International, vol. 2014, 537501.https://doi.org/10.1155/2014/537501

Digital Object Identifier (DOI):10.1155/2014/537501

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Download date: 20. Aug. 2021

https://doi.org/10.1155/2014/537501

https://doi.org/10.1155/2014/537501

https://www.research.ed.ac.uk/en/publications/fc72bbb1-4cfa-4450-bbb2-ae4786e2897f

Research ArticleAntibiotic Treatment Response of Chronic LungDiseases of Adult Sheep in the United Kingdom Based uponUltrasonographic Findings

Phil Scott

Division of Veterinary Clinical Sciences, R(D)SVS, University of Edinburgh, Easter Bush, Roslin, Midlothian EH25 9RG, UK

Correspondence should be addressed to Phil Scott; [email protected]

Received 9 December 2013; Accepted 5 May 2014; Published 27 May 2014

Academic Editor: Suresh Tikoo

Copyright © 2014 Phil Scott. This is an open access article distributed under the Creative Commons Attribution License, whichpermits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Examination of the lungs of adult sheep with chronic respiratory diseases was readily achieved using both 5MHz linear andsector scanners. Superficial lung abscesses in eight sheep appeared as anechoic areas containing multiple hyperechoic dotsbordered distally by a broad hyperechoic capsule. Unilateral fibrinous pleurisy (2 sheep) appeared as an anechoic area containinga hyperechoic latticework. Ovine pulmonary adenocarcinoma (OPA) lesions appeared as sharply demarcated hypoechoic areas inthe lung parenchyma initially in the cranioventral lung lobes (21 sheep) with lesions also present in the caudodorsal diaphragmaticlobe (11 sheep); abscesses and areas of calcification within the OPA tumourmass were also identified. Daily treatment with procainepenicillin for 30 consecutive days was successful in both sheep with unilateral fibrinous pleurisy and six sheep identified withsuperficial lung abscessesmeasuring 2–8 cm in diameter; only one of two sheepwithmore extensive lesions recovered. Auscultationof the chest failed to detect adventitious sounds in any of the ten sheep with lung abscesses; normal breath sounds were reducedover the area of fibrinous pleurisy; no pleuritic rubs were heard. Wheezes and crackles auscultated in some OPA cases and did notcorrelate well with lesions detected ultrasonographically.

1. Introduction

An aetiological approach to the diagnosis, treatment, andcontrol of respiratory diseases affecting sheep is often adoptedin review articles [1] and book chapters [2, 3] but suchprecise classification is unrealistic in most general veterinarypractice situations because of cost and access to specialisedlaboratory facilities. Clinical signs vary with the stage of therespiratory disease process and are not pathognomonic forparticular aetiological agents [4]. Terms such as “chronicpasteurellosis” are commonly used to describe respiratorydisease associated with weight loss with the recommendationof oxytetracycline therapy but there is little clinical evidencefor such a diagnosis. Furthermore, detailed gross necropsiesundertaken on farm prove difficult to interpret especiallywhen complicated by autolytic change; histopathologicalexamination is not often undertaken for cost reasons.

Individuals with chronic respiratory diseases are inpoorer body conditions and have a higher respiratory ratethan other sheep in the group [5]. The accuracy by whichauscultation of the chest, as part of the standard veteri-nary examination, can detect, localise, and differentiate lungpathology has been questioned following comparison ofadventitious sounds auscultated over normal lung areas andlesions of OPA [6]. Moderate to severe coarse cracklesdetected in advanced cases of OPA were audible over a largerarea than lesion distribution identified during ultrasoundexamination and confirmed later at necropsy [5].

Publication of auscultated sounds recorded over specificrespiratory tract pathologies, defined during simultaneousultrasonographic investigation, has allowed clinicians toassess the value of auscultation of the chest performedas part of the standard veterinary clinical examination ofsheep [5, 7] and cattle [8]. Auscultation did not detect any

Hindawi Publishing CorporationVeterinary Medicine InternationalVolume 2014, Article ID 537501, 5 pageshttp://dx.doi.org/10.1155/2014/537501

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2 Veterinary Medicine International

abnormal sounds in sheep with lung abscesses; unilateralpyothorax and marked fibrinous pleurisy caused attenuationof sounds relative to the contralateral normal lung.No soundsresembling the description of pleural frictions rubs wereheard in cases of marked fibrinous pleurisy [5].

While ultrasonographic examination of the chest in cattleand sheep has been routinely undertaken in some veterinaryschools for many years [9], this adjunct to clinical examina-tion also has great potential in farm animal practice becausethe examination takes only 5 minutes and does not involveany laboratory fees. Many chronic respiratory infections ofruminants are not accurately diagnosed, and such cattle andsheep do not receive the correct antibiotic treatment [10, 11].

This paper describes the antibiotic treatment response insheep with chronic lung diseases where the diagnosis wasbased upon ultrasonographic examination of the lungs using5MHz linear and sector scanners; no account was takenof auscultation findings. Lung pathologies were confirmedin those animals that failed to respond to treatment andwere euthanased for welfare reasons. Necropsy examina-tions allowed comparison between sonographic findings andpathological changes.

2. Materials and Methods

The thirty one sheep included in this study originatedfrom the University of Edinburgh’s first opinion ambulatorypractice and cases were referred by local veterinary practices.This study covered a two-year period (October 2011–October2013 inclusive). To mimic the time constraints faced by farmanimal practitioners, ultrasonographic examination of bothsides of the chest, including skin preparation, totalled nomore than 5 minutes for each type of ultrasound scanner andoften took less time. Ultrasonographic examination of thechest was undertaken using both 5.0MHz sector and lineartransducers connected to a real-time, B-mode ultrasoundmachine (Aloka and BCF Technology Miniscan).

A 5 cm wide strip of skin was shaved on both sides ofthe thorax extending in a vertical plane from the point ofthe elbow to the caudal edge of the scapula correspondingto the 6th or 7th intercostal spaces. The prepared skinoverlying the chest wall can be freely moved 3 cm whichallowed examination of the caudal aspect of the lung field.The skin was soaked with warm tap water then ultrasound gelliberally applied to the wet skin to ensure good contact. Thetransducer head was firmly held at 90∘ to the skin overlyingthe intercostalmuscles of the 6th or 7th intercostal spaces andthe thorax was examined in the longitudinal (vertical) plane.The relatively large linear probe head was held on the chestwall at a slight angle to represent the angle of the intercostalspaces. It was important to visualise the echogenic (white)line of the normal visceral pleura at the most dorsal marginof the lung field before scanning the ventral areas of thechest. The visceral pleura was followed down the chest wallto identify the junction between normal lung and pathologywhere present.

Figure 1: 5MHz sector scanner. The probe head is at the top ofthe image; dorsal is to the left. Centimetre gradations are indicatedon the margin. The surface of normal aerated lung (visceral or pul-monary pleura) of normal sheep is characterized by the continuouswhite linear echo. Equally-spaced reverberation artefacts are oftenvisible below the visceral pleura.

The diagnosis of respiratory disease was confirmed atgross necropsy in 22 sheep. Bacteriology examinations werenot undertaken because of prior antibiotic therapy. Ultra-sonographic examination of 31 adult sheep with respiratorydiseases associated with weight loss included OPA (21),fibrinous pleurisy (2 cases), and superficial lung abscesses (8cases).

3. Results

3.1. Interpretation of Ultrasonographic Findings. The sono-grams are presented with the probe head at the top of theimage; dorsal is to the left and ventral to the right of theimage. Centimetre dot markers are displayed on the marginof the images and should be consulted to ascertain thedepth of field presented. The chest wall of adult sheep wasapproximately 1–1.5 cm thick. An air interface, created byaerated lung parenchyma reflects soundwaves and appears asa brightwhite (hyperechoic) linear echo.The sonogrambelowthe white linear echo may contain equidistant reverberationartefacts which are of no clinical significance. The areavisualized below the linear echo, including the reverberationartefacts, does not represent lung parenchyma; thus the initialultrasound machine setting with a 5MHz sector transducerwas 8 cm which examined approximately 1–1.5 cm of chestwall then pleurae and superficial lung parenchyma. The5MHz linear transducer used had a field depth of 7–9 cm.

The surface of normal aerated lung (visceral or pul-monary pleura) was characterized by the uppermost whitelinear echowith equally-spaced reverberation artefacts belowthis line (Figure 1). Careful placement of the large linearprobe head was necessary to avoid the ribs (Figure 2). Innormal adult sheep (around 50–80 kg) the visceral pleurawas observed moving approximately 3mm in a verticalplane during respiration. Comet-tail artefacts represent aseries of closely-spaced discrete echoes indicating the focalaccumulation of a small amount of highly reflective material,often gas bubbles. The chest wall was approximately 1–1.5 cmwide.

Veterinary Medicine International 3

Figure 2: 5MHz linear scanner. The dorsal (left) half of the probehead is positioned over a rib causing shadowing; normal lung surfaceis apparent ventrally (right).

Figure 3: 5MHz sector scanner. 2 cm diameter pleural abscessappear as anechoic areas containing numerous hyperechoic dotsbordered distally by broad hyperechoic concave lines representingthe capsules.

3.2. Superficial Lung Abscesses. The hyperechoic linear echorepresenting the normal visceral pleura was lost with superfi-cial lung abscess which appeared as an uniform anechoic areacontaining many hyperechoic dots representing gas echoesbordered by a broad concave white abscess capsule (Figures 3and 4). The abscess extended for 7 cm from the chest wall inFigure 4.

3.3. Fibrinous Pleurisy. The visceral pleura appeared broaderand more hyperechoic than normal in one sheep due toacoustic enhancement by the pleural exudate (Figure 5) withfibrin extending to 3 cm present on the parietal and visceralpleurae. The visceral pleura could not be imaged in onesheep because the 7 cm wide anechoic area containing ahyperechoic fibrinous matrix extended beyond the depthrange of the linear scanner (Figure 6).

3.4. Ovine Pulmonary Adenomatosis (OPA). The first indica-tion of change in the lung parenchyma caused byOPAwas theabrupt loss of the bright linear echo formed by normal aeratedlung tissue (visceral or pulmonary pleura) to be replaced bya large hypoechoic area in the ventral margins of the lung

Figure 4: 5MHz sector scanner. Sonogram of a large lung abscesswhich extends 8 cm into the lung parenchyma.

Figure 5: 5MHz sector scanner.The visceral pleura appears broaderand more hyperechoic than normal due to acoustic enhancementby the pleural exudates with fibrin extending to 3 cm present on theparietal and visceral pleurae.

Figure 6: 5MHz linear scanner. The anechoic area containing ahyperechoic fibrinous matrix extends beyond the 7 cm depth rangeof the linear scanner.

4 Veterinary Medicine International

Figure 7: 5MHz linear scanner. Abrupt loss of the bright linear echoformed by normal aerated lung tissue (visceral or pulmonary pleura)to be replaced by a large hypoechoic area in the ventral lung.

Figure 8: 5MHz sector scanner. Abrupt loss of the bright linear echoformed by normal aerated lung tissue (visceral or pulmonary pleura)to be replaced by a large hypoechoic area in the ventral lung.

lobes at the 5th or 6th intercostal spaces (Figures 7 and 8).Thedorsal margin of sonographic change representing that theextent of theOPA lesionwas similar for either 5MHz linear orsector scanners.The hypoechoic areas, corresponding to lungtissue invaded by tumour cells causing consolidation (Figures7 and 8), allowed the distribution of the OPA lesions to beaccurately defined during the ultrasonographic examination.Focal hyperechoic areas, identifiedwithin themore cellularly-dense hypoechoic areas, represented large airways. Abscesseswere readily identified within the tumour mass of severalOPA cases; shadowing was attributed to fibrosis/calcificationof necrotic centres within the tumour (Figure 9).

Consecutive daily treatment with procaine penicillin for30 days was successful in all six sheep identified with pleu-ral/superficial lung abscesses measuring 2–8 cm in diameter;only one of two sheep with more extensive lesions recovered.

Figure 9: 5MHz sector scanner. 2 cm diameter abscess dorsally (toleft) within the OPA tumour mass; shadowing was attributed tofibrosis/calcification of a necrotic centre within the OPA lesion.

4. Discussion

Chronic bacterial infection of the respiratory tract in sheepusually presents with weight loss over several weeks/monthsand an increased respiratory rate [11]. A wide range ofdescriptors has been used to describe abnormal lung soundsin sheep including increased vesicular sounds for a ramwith severe chronic suppurative pleuropneumonia [12] andwheezing, rubbing vesicular, and murmuring sounds insheep with bacterial respiratory infections, followed byabsence of residual bronchial catarrh in the same sheepduring recovery [13]. Authors in more recent papers [14,15] have limited their descriptions of abnormal ausculta-tion findings of the respiratory tract to their distributionrather than character. The present study concurs with earlierpublished findings [5] that auscultation does not detectany abnormal sounds in sheep with lung abscesses; markedfibrinous pleurisy caused attenuation of sounds relative tothe contralateral normal lung and no sounds were heardresembling the description of pleural frictions rubs.

Ultrasonographic examination of the chest accuratelydefined superficial lung pathology in agreement with pre-vious work [16, 17]. Ultrasonography was most helpful inthe definitive diagnosis of superficial lung abscesses wherethe anechoic areas containing multiple hyperechoic dotsbordered distally by a broad hyperechoic capsule werereadily detected but generated no adventitious lung sounds.Daily treatment with procaine penicillin for 30 days wassuccessful in all six sheep identified with pleural/superficiallung abscesses measuring 2–8 cm in diameter; only one oftwo sheep with more extensive lesions recovered. Successwas defined as a rapid return to normal appetite, markedimprovement in body condition, and normal respiratory rate.Penicillin is the antibiotic of choice for chronic respiratorydisease in cattle and sheep because of the frequent isolation ofArcanobacterium pyogenes [11, 18].Arcanobacterium pyogeneswas the most common bacterial isolate from chronic suppu-rative pneumonia cases in cattle and such chronic infectionswere treated with a 4–6-week course of procaine penicillinwith reasonable success [8]. A 4–6-week duration of dailypenicillin injections is necessary because of the chronicityof infection and time-dependent action of this antibiotic

Veterinary Medicine International 5

[11]. Other antibiotic treatments could include ceftiofur,amoxicillin, and amoxicillin/clavulanic acid combination butthese regimens would prove considerably more expensive.

Lesions of ovine pulmonary adenocarcinoma (OPA)were sharply demarcated sonographically from normal lungwhere the hypoechoic areas extended 6–8 cm into the lungparenchyma in the cranioventral lung lobes and had thesonographic appearance of liver (hepatoid change). Suchlesions cannot be accurately delineated by auscultation find-ings alone [5, 6]. The ultrasonographic diagnosis of OPAwas confirmed at necropsy in all 21 cases in the presentstudy; there were no false positive diagnoses. Ultrasoundexamination may play an important role in identifying OPAlesions and help prevent spread in the UK both for economicand animal welfare reasons.

5. Conclusions

Accurate identification and distribution of pleural and super-ficial lung pathology necessitated ultrasonographic examina-tion; auscultation failed to identify common lesions includingOPA. With some experience, systematic ultrasound exam-ination of the ovine chest takes no more than 5 minutes.Long-term penicillin therapy was successful in 7 of 8 casesof pleural/superficial lung abscesses.

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper.

References

[1] S. Bell, “Respiratory disease in sheep 1. Differential diagnosisand epidemiology,” In Practice, vol. 30, no. 4, pp. 200–207, 2008.

[2] E. Bellknap, “Diseases of the respiratory system,” in Sheep andGoat Medicine, D. G. Pugh, Ed., pp. 107–128, W. B. Saunders,Philadelphia, Pa, USA, 2002.

[3] W. Donachie, “Pasteurellosis,” inDiseases of Sheep, I. D. Aitken,Ed., pp. 224–235, Blackwell, Oxford, UK, 2007.

[4] N. D. Sargison and P. R. Scott, “The implementation and valueof diagnostic procedures in sheep health management,” SmallRuminant Research, vol. 92, no. 1–3, pp. 2–9, 2010.

[5] P. Scott, D. Collie, B. McGorum, and N. Sargison, “Relationshipbetween thoracic auscultation and lung pathology detected byultrasonography in sheep,”Veterinary Journal, vol. 186, no. 1, pp.53–57, 2010.

[6] C. Cousens, M. Graham, J. Sales, and M. P. Dagleish, “Evalu-ation of the efficacy of clinical diagnosis of ovine pulmonaryadenocarcinoma,” Veterinary Record, vol. 162, no. 3, pp. 88–90,2008.

[7] P. R. Scott, “Lung auscultation recordings from normal sheepand from sheep with well-defined respiratory tract pathology,”Small Ruminant Research, vol. 92, no. 1–3, pp. 104–107, 2010.

[8] P. R. Scott, “Clinical presentation, auscultation recordings,ultrasonographic findings and treatment response of 12 adultcattle with chronic suppurative pneumonia,” Irish VeterinaryJournal, vol. 66, article 55, 2013.

[9] P. R. Scott andM. E. Gessert, “Ultrasonographic examination ofthe ovine thorax,”Veterinary Journal, vol. 155, no. 3, pp. 305–310,1998.

[10] P. R. Scott, “The role of ultrasonography as an adjunct to clinicalexamination in sheep practice,” Irish Veterinary Journal, vol. 61,no. 7, pp. 474–480, 2008.

[11] P. R. Scott, “Treatment and control of respiratory disease insheep,” Veterinary Clinics of North America, vol. 27, no. 1, pp.175–186, 2011.

[12] U. Braun, M. Fluckiger, D. Sicher, and D. Theil, “Suppurativepleuropneumonia and a pulmonary abscess in a ram: ultra-sonographic and radiographic findings,” Schweizer Archive furTierheilkunde, vol. 137, pp. 272–278, 1995.

[13] F. Naccari, F. Giofre, M. Pellegrino, M. Calo, P. Licata, and S.Carli, “Effectiveness and kinetic behaviour of tilmicosin in thetreatment of respiratory infections in sheep,”Veterinary Record,vol. 148, no. 25, pp. 773–776, 2001.

[14] V. S. Mavrogianni and G. C. Fthenakis, “Efficacy of difloxacinagainst respiratory infections of lambs,” Journal of VeterinaryPharmacology and Therapeutics, vol. 28, no. 3, pp. 325–328,2005.

[15] J. Skoufos, G. Christodoulopoulos, I. A. Fragkou et al., “Efficacyof marbofloxacin against respiratory infections of lambs,” SmallRuminant Research, vol. 71, no. 1–3, pp. 304–309, 2007.

[16] P. R. Scott, “Thoracic ultrasonography as an on farm adjunctto clinical examination on farm,” In Practice, vol. 31, no. 9, pp.446–453, 2009.

[17] P. R. Scott and N. D. Sargison, “Ultrasonography as an adjunctto clinical examination in sheep,” Small Ruminant Research, vol.92, no. 1–3, pp. 108–119, 2010.

[18] E. K. Barbour, N. H. Nabbut, S. K. Hamadeh, and H. M. Al-Nakhli, “Bacterial identity and characteristics in healthy andunhealthy respiratory tracts of sheep and calves,” VeterinaryResearch Communications, vol. 21, no. 6, pp. 421–430, 1997.

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